Document the host as a git checkout

/opt/ergosteur is now a checkout rather than a directory kept in step by scp,
so deploying is a pull.

Records why the remote is HTTPS rather than SSH: the repository is public, so
the host needs no credentials and no deploy key, and in exchange it cannot
push, which is the right shape for a deploy target.

Also notes that git carries the executable bit, since a script committed
without it now reaches the host non-executable and breaks any unit using it as
ExecStart. That failure mode did not exist while deploying by scp, which
carries the mode from the working copy regardless of what git records.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

README.md

@@ -3,8 +3,8 @@
 Host-side tooling for a Proxmox VE node: cloud-init template building, IPMI fan
 control, UPS/NUT setup, and a few odds and ends.
 
-This repository mirrors `/opt/ergosteur` on the Proxmox host. Nothing here is
-live until it is copied across — see [Deploying](#deploying).
+`/opt/ergosteur` on the Proxmox host is a checkout of this repository. Nothing
+here is live until the host pulls — see [Deploying](#deploying).
 
 ## Cloud-init templates
 
@@ -150,16 +150,28 @@ repository.
 
 ## Deploying
 
-`/opt/ergosteur` on the host is a plain directory, not a git checkout, so
-changes have to be copied over and will not appear from a `git pull`:
+`/opt/ergosteur` is a checkout of this repository, so deploying is a pull:
 
 ```sh
-scp build-cloudinit-template.sh update-image-pins.sh root@pet630:/opt/ergosteur/
+ssh root@pet630 'git -C /opt/ergosteur pull'
 ```
 
-Unit files under `systemd-system/` are mirrored to `/opt/ergosteur` for
-reference, but systemd reads them from `/etc/systemd/system`. Changing one
-means updating both and running `systemctl daemon-reload`.
+The remote is the HTTPS URL, not SSH. The repository is public, so the host
+needs no credentials and no deploy key; the trade-off is that it cannot push,
+which is what you want of a deploy target. Commit here, pull there.
+
+Local configuration under `conf/` is gitignored and survives a pull untouched.
+
+Two things to keep in mind:
+
+Unit files under `systemd-system/` are in the checkout, but systemd reads them
+from `/etc/systemd/system`. Changing one means copying it across and running
+`systemctl daemon-reload`; a pull alone changes nothing.
+
+The executable bit is carried by git, so a script committed without it will be
+non-executable on the host and any unit with it as `ExecStart` will fail to
+start. `git update-index --chmod=+x <file>` fixes a file already committed
+without it.
 
 ## Conventions